Recently, in building structure formed by concrete such as a tunnel, an accident in which concrete flakes comes into question and the enhancement of the quality of concrete building structure is severely demanded. To realize it, technique for promptly realizing the quality checking of building structure at a low cost is essential. Therefore, many methods of semiautomatically inspecting the quality of building structure nondestructively by an external inspection device are proposed.
In the meantime, a method of building various sensors in building structure beforehand when the building structure is constructed, constantly measuring/monitoring physical quantity such as stress by the sensors and monitoring the quality of the building structure or monitoring systems are also proposed. As in these monitoring systems, quality judgment is theoretically substantially automated, labor for quality judgment can be reduced.
Of these, for example, in a nonpatent document 1, an idea that an optical fiber sensor which can sense strain applied to itself is installed in building structure and stress applied to steel structure supporting the building structure is constantly monitored to utilize for the assurance of the earthquake-proof performance of the building structure is disclosed.
In the meantime, in a patent document 1, an idea that a strain gauge is laid on a reinforcing bar, the electric resistance of the strain gauge is measured and the quality of building structure is monitored at real time is disclosed. According to this document, stress in the building structure can be measured by the strain gauge and the result of monitoring can be utilized for maintenance and others. Though the concrete configuration is not described, an idea that a pH sensor is utilized for judging a degree of the deterioration of building structure is also disclosed.
Further, in a nonpatent document 2, a system that a sensor and a wireless installation are integrated and data detected by radio can be transmitted to external measurement equipment and others and can be monitored is disclosed. Concretely, an example that in a monitoring system in which a small-sized radio module the power consumption of which is little and a sensor that can detect vibration such as an acceleration sensor are integrated, a response to an earthquake wave in building structure such as an office building, that is, the earthquake-proof performance is measured is introduced.
Further, in a nonpatent document 3, it is disclosed that a floor, a wall and a human body constantly vibrate though the vibration is minute and they normally have the energy density of −mW/cm3.
Besides, in a nonpatent document 4, the configuration of an electric power generator that converts minute vibrational energy disclosed in the nonpatent document 3 to electric energy is disclosed.
In a patent document 2, the configuration of a pressure sensor (a strain gauge resistance type) that can be produced in a semiconductor process is disclosed.
Further, in a patent document 3, the configuration of a pressure sensor (an electrostatic capacity type) that can be similarly produced in a semiconductor process is disclosed.
Further, in a nonpatent document 5, ultra wide band (UWB) technique which is an ultra wide band telecommunication system is disclosed. As disclosed in this document; UWB technique enables telecommunication at ultralow power consumption. This document discloses that high-precision positional detection and the measurement of distance can be realized.
Further, in a nonpatent document 6, various factors that determine the strength of concrete are disclosed. Particularly, in this document, it is disclosed that a management period (hereinafter called curing) in which hydration proceeds after concrete casting and the strength of the concrete is manifest has a great effect upon the strength of the concrete. Concretely, information that heat caused in hydration has a bad effect upon the manifestation of strength is disclosed.
Besides, in a nonpatent document 7, it is described that a degree of the proceedings of the corrosion of a reinforcing bar in concrete can be estimated based upon a value of the electric resistance of concrete.
Further, in a nonpatent document 8, the details of the transmission characteristic of an electromagnetic wave in concrete are described.
[Patent Document 1]
Japanese published unexamined patent application No. 2002-38723
[Patent Document 2]
Japanese published unexamined patent application No. Hei11-121766
[Patent Document 3]
Japanese published unexamined patent application No. 2001-99734
[Nonpatent Document 1]
http://www.mita.sd.keio.ac.jp/papers/index.htm(d own load date:2002.08.01; Proc. Second International Workshop on Structural Health Monitoring, 1999, pp. 56 to 67 corresponds to the content of the URL)
[Nonpatent Document 2]
Nikkei Electronics, Jul. 17, 2002, pp. 37
[Nonpatent Document 3]
IEEE Computer July 2000, pp. 42 to 48
[Nonpatent Document 4]
IEEE TRANSACTIONS ON VERY LARGE SCALE INTEGRATION SYSTEMS, VOL. 9, NO. 1, FEBRUARY 2001, pp. 64 to 75
[Nonpatent Document 5]
Nikkei Electronics Mar. 11, 2002, pp. 55 to 66
[Nonpatent Document 6]
“Illustrated concrete” published by Ohm, pp. 95 to 111
[Nonpatent Document 7]
99′ annual report published by Power Central Research Institute, pp. 92 to 93
[Nonpatent Document 8]
http://www.tuat.ac.jp/˜masa/study-j.html